ponents discredit nonhuman mentality because they perceive the situation solely through the human lens: "The relatively simple content of animal thoughts and subjective feelings is almost certainly relevant to the animal's own situation rather than to human concerns" (Griffin, 1992, p. 19).
Although animals lack many of the intellectual abilities of human beings, it is the basic similarity between the two that forms the crucial issue. The foundation of this basic similarity is that both human and nonhuman creatures are each "the experiencing subject of a life," the value of which can be communicated (Regan, 1989, p. 111).
Critics of the animal behaviorist point of view contend that evidence of animal thinking is apparent by observation of certain exchanges of signals between two or more animals. One of the clearest examples of communication in the presence of other animals is the alarm signal. Studies of vervet monkeys have uncovered differentiation in alarm calls which prompts differentiation in response from the audience: "This would presume a degree of control over production of alarm calls" (Marler and Mitani, 1988, p. 9).
The vervet monkey gives three distinct calls to distinguish among leopard, martial eagle, and python predators. Upon hearing the leopard call vervet monkeys scurry into trees, but since leopards are excellent climbers, the monkeys know to take refuge on the slenderest branches. Such an evasive tactic would make the monkeys easy prey for martial eagles, however. So in response to the eagle alarm call the monkeys hide in thick vegetation near a tree trunk or at ground level. The python alarm call prompts the monkeys to rise on their hind legs and survey the ground to determine the most favorable escape route.
Critics of the ability of the vervet monkey to differentiate danger calls contend that the evasive strategies of the audience are based on cuing. The fleeing monkeys adapt their be...